Method for mounting a casing shoe on a drilling appatatus

ABSTRACT

A method for mounting a casing shoe ( 4 ) around a cylindrical drilling apparatus ( 2 ), which shoe is used by drilling and pulled in the ground on drilling, whereby shoe ( 4 ) and drilling apparatus ( 2 ) can in the installed position rotate with respect to one another and move a certain distance axially with respect to one another, when shoulder ( 8 ) in the shoe is in transverse groove ( 9 ) on the periphery of the drilling apparatus and the groove is determining the length of the axial motion. The cylindrical shoe ( 2 ) is shrunk in order to make its diameter smaller around a spot in drilling apparatus ( 2 ) smaller than the outer diameter (Du), until through shrinking the outer diameter of the shoe has become smaller than the outer diameter (Du) of the drilling apparatus.

[0001] The invention relates to the mounting of a casing shoe around a cylindrical drilling apparatus, which shoe is used by drilling and pulled into the ground on drilling.

[0002] Previously known, among other things, from Finish patent specification 86571 is a casing shoe around a cylindrical drill where on the drill periphery there is a grooving, in which the welded ring of the casing shoe is installed. The drill can rotate with respect to the ring and also move axially determined by the groove. The ring is formed of two halves by welding in the groove as a complete ring, further the ring is welded on the casing or the shoe.

[0003] The ring to be fitted in the groove must be of made two halves so that it can be installed in the groove, or the whole shoe must be cleaved longitudinally as equal halves and welded together around the drilling apparatus in order to produce a shoulder to restrict axial motions.

[0004] The solutions are complicated, since a part of the welds must be done in joints in a narrow space, the welds twist the shoe construction and the welded joint is not dependable by heavy loading. In percussive drilling apparatuses the shoe is for fatigue loading.

[0005] By means of the method according to the invention the shoe has no welds, since the shoulder in the shoe, is produced by turning or shaping. The method solves all problems and the method is characterized in what is presented in the patent claims.

[0006] The advantage of the invention is a fast and dependable assembly resulting in a circular shoe. Deformations due to welding are avoided and since the shoulder is produced by turning, it can be made to match exactly the counterface in the groove in the drilling apparatus.

[0007] In the following the invention is disclosed with reference to the enclosed drawings, where

[0008]FIG. 1 shows the shoe to be pushed into the tool, and the drilling apparatus

[0009]FIG. 2 shows the shoe shrunk in the tool around the drilling apparatus.

[0010]FIG. 3 shows the openable ring utilized for mounting.

[0011]FIG. 4 shows shrinking of shoe by means of clamp jaws.

[0012]FIG. 1 is a drilling apparatus furnished with a transverse groove 9, into which the shoulder 8 of shoe 4 is to be fitted. Further, the whole shoe 4 should be shrunk to a diameter size distinctively smaller than the outer diameter size Du of drilling apparatus 2 so that the shoe could advance in the drilled borehole. The casing to be pulled into the borehole is welded as a butted joint or a lap joint in the rear edge of the shoe.

[0013] The shoe is turned to such a diameter that it can be slid into a position around the drilling apparatus as shown in FIG. 1. In addition, in groove 9 of drilling apparatus 2 a two-piece ring as per FIG. 3 is placed, which by means of joint 7 can be both fitted in and taken off groove 9.

[0014] Tool 5 is a shrinking tool comprised of a conical portion 6 that causes the shrinking of the shoe. By means of rammer 1 the drilling apparatus and the shoe are pressed into tool 5 till shoe 4 is fully in the cylindrical portion Ds of the tool. The shoe is shrunk to a diameter size of Ds, fitted to be distinctively smaller than Du, which is the diameter size of the drilling apparatus and also the borehole diameter. When in groove 9 the ring 3 is used, it can be seen from FIG. 2 that shrinking can be carried out by pushing drilling apparatus 2 and, in spite of its bigger diameter the drilling apparatus does not yet reach the conical surface 6 of tool 5, even though shoe 4 has not fully passed the conical surface. Pushing can be stopped at this point and the shoe and drilling apparatus pushed back from the tool. Shoe 4 has then become formed through shrinking to its diameter size Ds and locked by means of shoulder 8 into groove 9, and the joint is ready.

[0015] The shoe shrinkage is produced by a tool and the tool dimensioned so that after shrinking there will remain between shoe a clear sliding fit. The sliding fit allows mutual rotation and axial motion between shoe and drilling apparatus. However, by means of the solution the shoulder 8 is locked in groove 9 to endure loads caused by pulling the casing.

[0016]FIG. 4 shows the shrinking of shoe 4 by multi-jaw squeezing with the shoe in proper position around the drilling apparatus. Shoulder 8 takes then its place in groove 9.

[0017] The shoe is shrunk ab. 2 to 8% of the diameter in the embodiment, where the shoe retains it form during shrinking. Usually, the shoe is then shrunk all over. If the shoe is formed beforehand to a smaller diameter as to its rear edge, the shoe is shrunk at least on the portion, where the shoulder is formed. Shoe shrinking elsewhere is then not necessary. 

1. A method for mounting a casing shoe (4)around a cylindrical drilling apparatus (2), which shoe is used by drilling and pulled into the ground on drilling, whereby shoe (4) and drilling apparatus (2) can in the installed position rotate with respect to one another and move a certain distance axially with respect to one another, when shoulder (8) in the shoe is in transverse groove (9) on the periphery of the drilling apparatus and the groove determing the length of the axial motion, characterized in that at least a part of cylindrical shoe (2) is shrunk in order to make its diameter smaller around a spot in the drilling apparatus smaller than the outer diameter (Du) of drilling apparatus (2) on which there is the transverse groove (9), until the outer diameter of the shoe has through shrinking become smaller than the outer diameter (Du) of the drilling apparatus and/or the formed shoulder is in groove (9).
 2. A method according to claim 1 characterized in that shoe (4) including shoulder (8) retain their shape during shrinking.
 3. A method according to claim 1 and 2 characterized in that shoe (4) is shrunk by means of many clamping jaws (10) formed to correspond to the shoe (4) outer surface.
 4. A method according to claim 1 and 2 characterized in that the shoe is shrunk in forcing the shoe into a tool (5) that has a diminishing conical portion (6).
 5. A method according to any of the previous claims 1-4 characterized in that in order to carry out the shrinking stage, into groove (9) a detachable ring assembly (3) is placed, which steers the shoe (4) shoulder (8) to become shrunk in the backmost edge of groove (9) with respect to the drilling direction.
 6. A method according to claim 5 characterized in that on using the ring assembly (3) the drilling apparatus with shoe (4) is pushed into conical tool (5) until the shoe size is shrunk to the diameter size needed. 